Learning Forum

[YH]

Hello,

I calculate LES+Ffowcs Williams Hawkings model.

I noticed that we must use [m] to allocate the acoustic receiver position because the unit in the dialog box does not change (figure1), even I setted up unit system of length as [in]. So my question is what is the unit of the calculated acoustic pressure? Because I setted up the pressure unit system as [psi], I thought the acoustic pressure was also [psi]. But considering that the receiver position always uses SI unit, acoustic pressure is in [Pa]? And there's no discreption about unit in the result (figure2).

figure 1

figure2

[Rob]

Given the result above is around 190 atm if it is Pa I'd be checking the results & boundary settings too. 

[YH]

Hi Rob,

Thank you so much for the reply. I know the pressure is extreamly high whether it is in Pa or psi. I think this is beacuse of the receiver's position, since I set up the receivers close to the sound source.  In order to consider about this reason, the unit is important for me. 

I'm not sure if this acoustic model follows the Ansys Fluent unit system. I searched in the user guide, but it doesn't help me. Would you tell me the way to identify it? 

 

[Rob]

Report units tend to be SI so I suspect it's Pa. Change the units in Fluent, run a time step and see whether the report changes. 

[YH]

I see. That's a good idea and I'll do that. Thank you so much. 

[YH]

I changed the pressure unit system and the result didn't change. So I think the acoustic pressure is in Pa. Thank you.